The present invention relates to brass alloys, more particularly, copper-zinc brass alloys which exhibit enhanced grain growth characteristics when modified with arsenic.
During the processing of brasses from which deep drawn shell casings and other articles are made, it is desirable to produce alloys of coarse grain size. The specific grain size which is desired is produced by controlling the recrystallization annealing treatment. In order to reduce the cost of heat treating, and to increase productivity and furnace life, it would be desirable to lower the temperature necessary to produce a desired grain size.
The use of arsenic as an alloying element in copper base alloys is well known for the purposes of dezincification and improving corrosion resistant characteristics. For example, arsenic has been added to admiralty brass, that is a copper-zinc-tin brass, in a range of 0.02 to 0.10 percent by weight to inhibit dezincification and enhance corrosion resistance. It has been found that arsenic, when added to copper-zinc-tin alloys, segregates to grain boundaries and thereby inhibits grain boundary related corrosion. It has been found that when the arsenic is segregated to the grain boundaries in copper-zinc-tin alloys, the grain growth characteristics of the alloy is retarded.
In addition to the above, arsenical copper, that is copper where arsenic is added in a range of from 0.15 to 0.50 percent by weight, has also been shown to have retarded grain growth. The presence of the arsenic is denoted by smaller grain sizes which leads to lower ductility unless annealing temperatures are raised. Likewise, arsenic has been added to aluminum bronze alloys to improve the corrosion resistant characteristics thereof but again grain growth retardation has been experienced.